Scott Dalziel and Ryan Wallace both scored twice as East Fife inflicted a heavy defeat on relegation-threatened Forfar, who slipped to just two points from the bottom of the Second Division table.
Dalziel put the visitors ahead with a clinical finish after latching on to Neil Janczyk's pass from the left in the 15th minute.
Janczyk was once again the provider three minutes later, his cross finding Wallace who headed into the top corner to double the Fifers lead.
Kevin Byers halved the deficit with a powerful strike after 32 minutes, but Wallace collected Darren Smith's pass eight minutes into the second half before firing past Forfar goalkeeper Greg Paterson to restore the away side's two-goal lead.
Substitute Craig Johnstone set up Dalziel to secure the win for Gordon Durie's team two minutes into injury time, condemning the hosts to their third defeat in four games.
Forfar: Paterson, McCulloch, Shaughnessy, Iain Campbell, Ross (Coyne 75), Bolocheweckyj, Byers (Ross Campbell 72), Fotheringham, Motion (Hegarty 64), Templeman, Hilson.
Subs Not Used: McKane, Gibson.
Booked: Iain Campbell.
Goals: Byers 32.
East Fife: Michael Brown, Durie, McCormack, Campbell, Ovenstone, Linn (Johnstone 78), Darren Smith (Muir 78), Janczyk, Robert Sloan (Hislop 85), Dalziel, Wallace.
Subs Not Used: Collier, McQuade.
Goals: Dalziel 15, Wallace 18, 53, Dalziel 90.
Ref: Frank McDermott